an arizona department of transportation -1 united states ... · 4 to this report, the total...

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11th International Bridge and Structures Management Conference

An Arizona Department of Transportation - United States Geological Survey Pilot Project 1

Blending Science and Engineering - Laguna Creek Bridge Bank Protection 2

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Submission date: March 1, 2017 6

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Word : 4,901 8

7 figures : 2, 250 9

0 tables : 10

Total : 7,151 11

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Submitted to 15

The Transportation Research Board 16

For Presentation 17

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Bank Protection Project Description: 21

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Steven Olmsted, M.S., M.Sc. (Corresponding Author) 23

Organization: Arizona Department of Transportation 24

Address: 1611 West Jackson, MD EM02, Phoenix, AZ, 85007 25

Phone: 602.712.6421 26

E-mail: [email protected] 27

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Rob Brantley, P.E., S.E. 29

Organization: Jacobs - Building & Infrastructure Division 30

Address: 101 North 1st Avenue, Suite 2600, Phoenix, AZ 85003 31

Phone: 602.650.4923 32


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Zahit Katz, P.E. 35


Address: 205 S. 17th Ave. Phoenix, AZ 85007 37

Phone: 602.712.7030 38

Email: [email protected] 39

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ADOT Resilience Program Description: 1

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Steven Olmsted 3


Address: 1611 West Jackson, MD EM02, Phoenix, AZ, 85007 5

Phone: 602-712-6421 6


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USGS Laguna Creek Pilot Project Description: 9

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Brandon Forbes 11

Organization: United States Geological Survey (USGS AzWSC) 12

Address: 520 N. Park Avenue, Suite 221 Tucson, AZ 85719 13

Phone: 520.670.6671 14


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Geoffrey Debenedetto 17

Organization: United States Geological Survey (USGS AzWSC) 18

Address: 2255 Gemini Drive, Flagstaff, AZ 86001 19

Phone: 928.556.7353 20


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ABSTRACT 1

Laguna Creek Bridge Scour Remediation, State Project Number H8913 01C, 2

Federal Aid No. 160-B(205)T, is a scour remediation project on the existing Laguna Creek 3

Bridge located in Arizona Department of Transportation’s (ADOT) Northeast District. Laguna 4

Creek Bridge is located on United States (US) Route 160, Tuba City-Four Corner Monument 5

Highway, MP 420.1, over Laguna Creek in Apache County, Arizona. The bridge is within the 6

boundaries of the Navajo Nation Reservation. This site is approximately twenty-five (25) miles 7

east of the Town of Kayenta, Arizona. This project was administered by ADOT, who maintains 8

the facility. The project scope consisted of installation of riprap gabion spur-dikes upstream and 9

downstream of the existing structure and along the bridge abutments, in an effort to mitigate 10

scour, provide bank protection, and reduce channel meandering at the bridge. 11

The original bridge structure was constructed in 1961 by the United States 12

Department of Interior. In 1984 the original bridge was retrofitted with barriers. During the 13

period from 2004 to 2008, bridge inspections identified excessive scour at both of the pier 14

locations. In 2012 a replacement bridge was constructed just to the south of the previously 15

existing bridge structure. Bridge abutments repairs and countermeasures were recommended, 16

but were found to be insufficient to address the current problem. Since then, inspection efforts 17

have continued to identify and monitor the accelerating meandering of the wash and subsequent 18

undercutting of the abutment fill. The goal of the project was to provide protection of the 19

existing bridge and roadway against the effects of local scour and severe channel meandering 20

just upstream and downstream of the bridge crossing. 21

In 2015 ADOT set out to develop a Statewide Stormwater Modeling program. The 22

effort was designed to centralize the Agency’s response to system wide water issues, introduce 23

next generation science and engineering modeling techniques (2-D hydrological and 3-D 24

visualization), advance risk-science-technology-engineering development goals, and launch the 25

Arizona DOT Resilience Program. The United States Geological Survey (USGS) Arizona Water 26

Science group was key to the new program and supplies ADOT direct (real-time) storm 27

monitoring and data collection, indirect (post-storm event monitoring and data collection), and 28

next generation hardware/software and surface water flow data collection capabilities. This 29

partnering effort would contribute to expediting and improving ADOT’s efforts in planning and 30

responding to incidents of flood, over-topping, system hotspots, hydraulic-related failure, and 31

extreme weather events in connection with 1) NEPA jurisdictional and wetland delineation and 32

streamlining 2) Highway stormwater runoff management 3) Evaluating scour potential and 33

countermeasure development at water crossings 4) Drainage structure siting, design and 34

construction 5) Response to Federal extreme weather regulatory activities. 35

The first of six pilot efforts to address different types of water exposure on ADOT’s 36

highway system were initiated in 2016. The Laguna Creek project was identified as the main 37

pilot to test a suite of USGS next generation technologies as they relate to transportation 38

infrastructure - LiDAR, UAS (drone), Rapid Deployment Streamgage, Non-Contact Velocity 39

Sensors, Video Camera and Particle Tracking Data Collection, 3-D Land Surface Models. 40

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BANK PROTECTION PROJECT 1

US 160 is classified as a Rural Principal Arterial Highway in ADOT’s Functional 2

Classification Map. It is located in the Federal Highway Administration (FHWA) National 3

Highway System. The original Laguna Creek Bridge (# 705) was constructed in 1961. This 4

bridge was replaced in 2012 (# 20001) with a single-span bridge, however, abutment bank 5

protection was not included in the project. Since completion of the bridge construction, Laguna 6

Creek has meandered resulting in a significant amount of undercutting of the fill slopes adjacent 7

to the bridge abutments. The work under this Scoping Letter is to analyze the existing bridge 8

conditions and provide scour remediation alternatives to prevent further erosion and protect the 9

bridge abutments and approaches. 10

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A listing of the original and subsequent construction projects that incorporated all 12

or part of the project segment are listed below: 13

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15 Figure 1. Project Hydraulic Report Final 16

Site Conditions 17

Laguna Creek originates at Tsegi Canyon and flows northeast. Soil in the watershed 18

is fine grained and susceptible to sediment transport at relatively low velocities. The US160 19

crossing is characterized by a meandering vertical bank channel (unstable). Laguna Wash has the 20

potential to adversely impact the US 160 structure at the following three locations: 1) Abutment 21

#1, 2) Abutment #2, and 3) the approach roadway west of the structure. The following aerial 22

photograph shows the existing channel and the historic scarring due to previous migrations of the 23

wash (old oxbows). 24

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26 Figure 2. Aerial SR 160 Laguna Creek Bridge 27

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Drainage Conditions 1

A Hydraulics Report for Laguna Creek Bridge was completed in May 2011 by 2

ADOT Bridge Group, Bridge Hydraulic Section (TRACS No. 160 NA H 7571 01C). According 3

to this report, the total watershed area for Laguna Creek Bridge is 848 square miles. Discharge 4

and water surface elevation are summarized below. The proposed bridge required 1 foot of 5

freeboard for the 50-year storm. The bridge soffit elevation is 4973.67. 6

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8 Figure 3. Project Hydraulic Report Final 9

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Proposed Improvements 11

In order to protect the existing bridge it is recommended that guide banks be 12

constructed to direct storm water through the structure. The guide banks will be constrained by 13

limited rights-of-way (200’ to the north of US 160 centerline and 100’ south of US 160 14

centerline). The area of disturbance (excavation limits) may not extend outside of the rights-of-15

way and the proposed improvements may not adversely impact the cultural site adjacent to the 16

structure. Team members evaluated several alternatives for the guide banks including: cement 17

stabilized alluvium (CSA), ADOT standard rail bank protection, gabion mattress, gabion basket, 18

grouted rip rap, rip rap, and sheet pile bank protection. 19

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Design Alternatives 21

Seven (7) design alternatives for Laguna Creek Bridge bank protection were 22

evaluated in this Scoping Letter. The preferred alternative was determined to be gabion baskets 23

(Alternative 1) due to the smaller area of disturbance, constructability, long-term bank protection 24

and lower cost relative to the other alternatives. Below is a description of four (4) of the 25

alternatives. The preliminary configuration of Alternative 1, Gabion Baskets is shown below 26

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Alternative 1: Gabion Baskets 28

Description: 29

This alternative consists of 3’ x 3’ x 6’ gabion baskets, filled with 4” to 8” nominal rock that will 30

be placed around the perimeter of the bridge abutments and approaches to prevent lateral stream 31

migration and bank protection. 32

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Conclusion: 34

The preferred alternative was determined to be gabion baskets. The use of gabions baskets 35

reduces the disturbance area, is constructible based on the site constraints, and is the most cost 36

effective of all of the alternatives considered in this scoping letter. Gabion baskets have the 37

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advantage of being constructible beneath the existing bridge, requiring only a small section of 1

concrete infill at the top of the new gabion wall where vertical clearance beneath the existing 2

bridge is less than approximately 5’. Rock suppliers have been located in southern Utah and in 3

the Phoenix area. 4

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Alternative 2: Driven Sheet Pile Bank Protection 6

Description: 7

This alternative consists of driving a continuous wall of sheet piling to the required scour 8

elevation plus the required embedment depth for the piling. Various pile sizes were considered. 9

Due to the height of material required to be retained by the piling, large pile sections such as AZ-10

24 and larger are required. It is also necessary to construct a 3- tiered wall system with the back 11

rows acting as buried tie-back walls. For the segment of protection directly below the bridge 12

there is insufficient vertical clearance to drive piling, so a separate type of wall such as gabion 13

baskets or a CSA wall would need to be constructed and connected to the sheet piles outside of 14

the bridge limits. 15

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Conclusion: 17

Sheet piles were eliminated due to high cost, difficulty of construction, and large area of 18

disturbance. 19

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Alternative 3: Cement Stabilized Alluvium (CSA) 21

Description: 22

This alternative constructs a compacted cementitious soil fill to create a hardened surface layer 23

that will prevent stream lateral migration and erosion due to scour. 24

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Conclusion: 26

CSA was determined not to be practical due to the limited space to operate large grading and 27

compaction equipment beneath the existing bridge. The area of disturbance exceeded the rights-28

of-way limit due to the flatter side slopes required for typical CSA construction. This alternative 29

is also the highest cost of the three constructible alternatives considered for the site. 30

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Alternative 4: Rail Bank Projection 32

Description: 33

This alternative uses ADOT standard Rail Bank Protection constructed around the perimeter of 34

the bridge abutments in a configuration similar to the Gabion basket bank protection alternative. 35

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Conclusion: 37

Rail bank projection is eliminated because the existing standard is not capable of providing more 38

than 10’ of vertical projection above existing grade. The vertical face requiring protection 39

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adjacent to the bridge abutments exceeds 20’ in most locations. Rail bank protection is not 1

constructible beneath the bridge due to insufficient vertical clearances. 2

3 Figure 4. Project Design Overview 4

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3 Figure 5. Looking downstream approaching the structure (notice the floating fence – upper right) 4

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6 Figure 6. Looking downstream from the structure 7

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Integration of USGS Technology for Future Design 1

Due to the emergency nature of this project the preliminary scoping was based largely on 2

hydraulic and geotechnical information obtained for the design of the replacement bridge 3

(#20001). In large part this is typical for many scour design projects; limited information is 4

available in the preliminary design stage when key decisions are made that impact the project 5

construction costs, durability, and long term maintenance costs. 6

The availability of real-time information has many beneficial impacts. The USGS information 7

allows planners and designers to view current channel configurations as well as to look at time 8

lapse information for comparison. On the Laguna Creek project our team was able to compare 9

current stream velocity and path with prior survey data and hydraulic studies for confirmation of 10

our assumptions of the long-term channel movement in the vicinity of the bridge. It will now be 11

possible to monitor the channel behavior with the bank protection in place to improve our 12

understanding of the protections long-term performance and potential refinements for future 13

designs. The velocity vector and flow limits data can be used to verify 1-D hydraulic models as 14

well as calibrate or verify 2-D hydraulic models early in the design process. This will enable 15

designers to progress more quickly through the design process while enhancing their confidence 16

in the results. 17

The availability of this information is valuable to owners and agencies in several ways. The 18

topographic and stream flow data can be obtained using drone-mounted photogrammetry. This 19

enables information to be cost effectively obtained over large areas and streamlines or eliminates 20

the permitting process required to obtain traditional field survey and stream flow data outside of 21

existing Right of Way limits. Software is available that allows this data to be transformed into 22

renderings that allow a quick visual interpretation of the site characteristics to facilitate 23

coordination among diversified staff and agencies. 24

This information also adds value for construction cost control. In a typical design-to- 25

construction cycle the topographic survey data is obtained as early in the design process as 26

possible. The construction project is then bid against the plans, specifications, and estimates 27

which are based on the original survey. It is often the case that stream migration, erosion or infill, 28

and changes in accessibility occur in the time period between the design survey and the 29

construction project award. These items can become change orders during construction as well as 30

result in delays for design changes to be produced. While not currently implemented, it should be 31

possible to utilize this hydraulic data to improve construction cost estimating and to mitigate 32

potential delays and funding shortfalls due to naturally occurring shifts in channel profiles. 33

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ADOT RESILIENCE PROGRAM 1

Transportation infrastructure is a complex system of assets required to deliver a 2

myriad of services and functions. As fiscal constraint for the development and rehabilitation of 3

such structures continues to be cost prohibitive, new and novel approaches to life cycle costing 4

and long term planning become paramount. In addition, the management of these infrastructure 5

systems has now evolved from a decentralized, project based focus to one that now encompasses 6

enterprise wide endeavors [1]. Three areas of concern for state DOTs and the main catalyst for 7

developing an ADOT Resilience Program involved how to: 8 9

Centralize to one operating area the unknown, erratic, and abrupt incidents of stormwater 10

and its contributors of flooding (overflow of water that submerges land), overtopping 11

(rise over or above the top), system hotspots (roadway flood prone history), hydraulic-12

related failures (structure failure mechanisms) 13

Introduce extreme weather adaptation to agency and engineering design processes and 14

establish transportation asset sensitivity to extreme weather 15

Handle scientifically-informed climate data downscaling as it relates to transportation 16

systems and development of an ADOT Climate Engineering Assessment for 17

Transportation Assets (CEA-TA) 18

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Flood Event - State of the Practice 20

Flooding, and the effects and impacts of flooding along transportation corridors, has 21

caused billions of dollars of damage and countless deaths. Technology currently exists to 22

accurately pinpoint those areas along a transportation corridor that are susceptible to flooding. 23

“Although there are tools . . . they have not yet been integrated to provide sufficient planning and 24

prediction information required by state DOTs to carry out flood planning, risk management, 25

mitigation, operations and emergency response activities.” Further research is needed to translate 26

the available technologies into a suite of tools and methods for use by decision makers [2]. 27

The largest hurdles for state DOTs in connection with flooding and risk assessment 28

tends to be the shortage of an end-to-end framework that addresses planning, risk management, 29

hazard mitigation, maintenance repairs, and life cycle projecting. This is particularly true when 30

an event or emergency has extensive cascading impacts. The main avenue to finding a solution is 31

to develop an approach that could funnel all these issues to one place for proper analysis within 32

the state DOT utilizing current technology, tools, and partnerships that could benefit the DOTs 33

[3]. 34

State DOTs generally utilize some form of flood frequency analysis to evaluate a 35

given asset. Design and response standards may not provide enough flexibility to unusual or 36

extreme weather occurrences. Certain assets may not require any special treatment, as available 37

data and standard design guidelines offer acceptable levels of mitigation. This is particularly true 38

when the asset is either at the largest, most monitored level, or is very small and maintenance 39

oriented. Issues arise when a non-monitored asset is overwhelmed, and when the best 40

representations of probability-distribution of floods equal to or longer than 2-years, no longer 41

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applies. The range for the confidence limits of that distribution is relatively tight, because in 1

general the fifty (50) largest floods are used to establish the best fit line for the asset [4]. 2

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Overtopping and System Hotspots – State of the Practice 4

NCHRP Synthesis 20-05 (46-16) completed in late 2016 with the objective to 5

produce “a state of the practice report on how the transportation community is protecting 6

roadways and mitigating damage from inundation and overtopping. The report documented ‘the 7

mechanics of damage to the embankment and pavement, analysis tools available, and design and 8

maintenance practices for embankment protection. The synthesis considered the inundation-only 9

condition of pavements and subgrades” [5]. The immediate risk of overtopping and inundation 10

(an overwhelming abundance) is an indication of how crucial that particular segment of roadway 11

within the system is to moving traffic. Determining how quickly that route can be up and running 12

again is essential to an efficiently functioning transportation system. In rural parts of Arizona it is 13

common to use vertical curves and to take advantage of natural low flow areas to address the 14

roadway prism drainage needs. To clarify, roadway overtopping generally begins when the 15

headwaters rise to the elevation of the roadway (as seen in Figure 7 below). The overtopping will 16

usually occur at the low point of a sag vertical curve on the roadway. 17

18 Figure 7. ADOT Cross Section 19

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Hydraulic-Related Failure - State of the Practice 21

Current industry practice looks to develop a “risk and reliability-based 22

methodology” that can be utilized to better link scour depth estimates to probability at the 23

crossing of rivers, washes, streams, and transportation assets. In addition, state DOTs need an 24

approach for determining a target or range of reliability for the service life of that asset that is 25

consistent and reasonable for the design load and resistance factors [3]. 26

Event uncertainty makes identifying probability from a limited number of flood 27

events and linking a range of reliability from those events challenging. The probability of 28

exceeding a design-scour-depth over the service life of a bridge additionally has a low 29

likelihood. Hydraulic parameters such as roughness coefficient, channel energy, and critical 30

shear stress also contain uncertainties. Inputs in hydraulic models estimate flood elevations and 31

velocities. Uncertainties in the estimates will translate to uncertainties in resulting calculations. 32

Changes in the wash structure over time such as upstream and downstream impacts, 33

surface water and groundwater wash-instability magnification effects (as seen in Figure 8 below) 34

drought, vegetation, bank erosion and sediment transfer are all factors which inject additional 35

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uncertainty. Supplementary data to more efficiently depict activity in the area is needed to limit 1

the amount of uncertainty in the estimates. A way to limit the uncertainty of all these conditions 2

and factors is the utilization of measured data such as high water marks, discharge 3

measurements, broad system sensors, water surface effects, and new usages of historical data. 4

Attempting to establish a repeatable process to address hydraulic-related failure and assessing 5

hydraulic, geomorphic, vegetation, construction, and maintenance impacts from those failures is 6

specific to the FHWA asset management MAP-21 guidance. 7

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9 Figure 8. Hydraulic-related failure monitoring due to ground water, channel energy, and altered flow 10

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In addition, FHWA guidance directs federally funded projects to incorporate risk into bridge 12

scour analyses and project development. It dictates that design efforts for new bridge foundations 13

should withstand “the effects of scour caused by hydraulic conditions from floods larger than the 14

design flood” [3]. 15

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Extreme Weather - State of the Practice 17

FHWA’s climate change and extreme weather vulnerability assessment pilot 18

projects collected a wide geographic sampling of vulnerabilities in the transportation asset 19

universe. Establishing transportation asset sensitivity to extreme weather can contribute to a 20

systematic approach to programming adaptive capacity strategies and asset life cycle 21

prioritization. These vulnerability assessments gather data on assets, identify characteristics and 22

sensitivities, analyze historical weather data, determine a usable climate projection model, and 23

through this iterative process develop a vulnerability framework [6,7,8]. 24

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Integrating risks based on the severity or consequence of an extreme weather 1

impact and determining the probability or likelihood it would occur to a specific asset at some 2

point now or many decades forward is challenging. But, even low likelihood risk assessment 3

modeling using historic, current, or 2050 / 2100 climate projection can allow state DOTs to 4

categorize assets by a low, moderate, or high rating. “The integrated risk is often represented by 5

a two-dimensional matrix that classifies risks into three categories (low, moderate, high) based 6

on the combined effects of their likelihood and consequence. An example matrix risk rating 7

matrix used by the San Francisco Pilot” is provided in Figure 8 below [7]. Risk application 8

within the context of this paper refers to the additional analysis undertaken to put a variety of 9

determined flows into a context of likelihood or future recurrence interval in relation to historic 10

peak-flow discharge. 11

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13 Figure 9. Risk Rating Matrix 14

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Resilience Building – ADOT State of the Practice 16

The reality of a changing climate means that transportation and planning agencies 17

need to understand the potential effects of changes in temperature, storm activity, and 18

precipitation patterns on the transportation infrastructure and services they manage. These 19

changes can result in increased heat waves, droughts, storm activity, early snowmelt, wildfires, 20

and other impacts that could pose new challenges for ADOT. The goal of the 2014 Preliminary 21

Study of Climate Adaptation for the Statewide Transportation System in Arizona study was to 22

establish a path for ADOT to continue working toward being more resilient, flexible, and 23

responsive to the effects of global climate change. The study identified, key individuals within 24

ADOT with decision making authority relevant in incorporating climate change adaptation in 25

planning, design, and operations, framed relevant literature and best practices for climate change 26

adaptation as relevant to the desert southwest, developed a research agenda for ADOT to further 27

http://www.fhwa.dot.gov/environment/climate_change/adaptation/publications_and_tools/vulnerability_assessment_framework/figure4.cfm

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understand the impacts of climate change on the agency, and identified key areas for further 1

research on climate change adaptation for ADOT’s statewide transportation system beyond the 2

scope of the initial study [8 - P.5]. 3

The 2014 effort led ADOT to participate in the FHWA Climate Change Resilience 4

Pilot program; the pilot effort assessed the vulnerability of ADOT-managed transportation 5

infrastructure to Arizona-specific extreme weather. Long term, ADOT sought to develop a multi-6

stakeholder decision-making framework – including planning, asset management, design, 7

construction, maintenance, and operations – to cost-effectively enhance the resilience of 8

Arizona’s transportation system to extreme weather risks. ADOT elected to focus on the 9

Interstate corridor connecting Nogales, Tucson, Phoenix, and Flagstaff (I-19, I-10, and I-17). 10

This corridor includes a variety of urban areas, landscapes, biotic communities, and climate 11

zones which present a wide range of weather conditions applicable to much of Arizona. The 12

project team examined climate-related stressors including extreme heat, freeze-thaw, extreme 13

precipitation, wildfire, and considered the potential change in these risk factors as the century 14

progresses. 15

As part of the pilot program, the study leveraged the FHWA Vulnerability 16

Assessment Framework customizing it to fit the study’s needs. The project team gathered 17

information on potential extreme weather impacts, collected datasets for transportation facilities 18

and land cover characteristics (e.g., watersheds, vegetation), as well as, integrated these datasets 19

to perform a high-level assessment of potential infrastructure vulnerabilities. Each step of the 20

process drew heavily on internal and external stakeholder input and feedback. This assessment 21

qualitatively addresses the complex, often uncertain interactions between climate and extreme 22

weather, land cover types, and transportation facilities—with an ultimate focus on potential risks 23

to infrastructure by ADOT District. Preliminary results were presented in focus groups where 24

ADOT regional staff provided feedback on the risk hypotheses developed through the desktop 25

assessment. The results of the assessment were, organized first by District, then by stressor, and 26

then further delineated by land cover types (e.g., desert) which are considered qualitative 27

potential factors that could either alleviate or aggravate the impacts of extreme weather 28

phenomena [9 – P. ES-1] 29

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2016 National Cooperative Highway Research Program (NCHRP) Project 15-61 31

This effort is in response to hydrological and hydraulic engineers need to address climate 32

change and engineering dynamics. In addition, the research problem statement goes on to 33

explain, in order to provide "hydraulics engineers with the tools needed to amend practice to 34

account for climate change, output from climate models must be downscaled and modified to 35

provide recommended changes to regional precipitation data for design events used by 36

hydraulics engineers. Collaborative efforts between climate scientists, hydrologists, hydraulic 37

engineers, and coastal engineers, are essential to producing these design inputs that are needed to 38

amend hydraulic designs. Incorporating the results of climate models will have very large cost 39

implications for future infrastructure. Overestimating the magnitude of peak flows suggested by 40

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climate models can result in costly over sizing of drainage infrastructure, while underestimating 1

may leave infrastructure vulnerable and their resultant flooding impacts on surrounding lands 2

and structures inadequately addressed” [10]. 3

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USGS PARTNERSHIP & LAGUNA CREEK PILOT PROJECT 6

Infrastructure in or near dryland river channels are susceptible to a variety of 7

geomorphologic and hydrologic hazards caused by floodwaters. Historically, many dryland 8

channels in northeastern Arizona were broad, shallow, and mainly un-vegetated. As a result, 9

floodwaters in the past were conveyed slowly and gently through stream channels and 10

surrounding floodplains at relatively low velocities and shallow flood depth. Today, many 11

dryland channels have changed dramatically and have become largely incised into the floodplain, 12

while the carved banks are being stabilized by vegetation, in many cases by nonnative tamarisk 13

(Tamarix ssp). The increase in bank stability may cause channels to incise deeper into 14

floodplains, leading to narrower, less sinuous stream beds that can potentially convey floods at 15

higher velocities. Additionally, channels in this region have the ability to convey and deposit 16

large amounts of sediment, and sediment volumes may become larger as flood velocities 17

increase. Ultimately, larger floods at higher velocities can erode the outside of channel bends 18

where velocities are typically high, and deposit sediment on the inside of bends where velocities 19

are naturally lower. This commonly causes channel migration, meander cutoff, and avulsion 20

[11]. Prior studies have found that river channel instability in arid and semiarid regions and 21

erosion caused by channel migration resulted in economic losses that were potentially five times 22

greater than potential flood inundation losses [12]. However, potential channel migration is 23

rarely accounted for in flood risk assessment [11]. 24

Channel erosion and deposition have occurred at Laguna Creek at State Highway 160 25

bridge site. The channel is incised into the floodplain, the banks on the outside of bends are 26

eroding, and clear evidence of past channel migration and meander cutoff can be seen just 250 27

feet downstream from the bridge structure. Additionally, any further erosion that occurs near the 28

roadway may impact the transportation infrastructure. This erosion caused the Arizona 29

Department of Transportation and the U.S. Geological Survey Arizona Water Science Center to 30

deploy multiple sensors and use new technologies to collect many different types of data to help 31

better understand the dynamic hydrologic conditions at the bridge site prior to construction 32

efforts. 33

The effort started with the deployment of real time hydrologic data collection equipment 34

to help form a baseline reference for the river conditions at the bridge. First, a rapid deployment 35

streamgage was installed on the bridge structure. This gage contains equipment that measures 36

river stage and surface velocity, which is telemetered to provide users with real time stream flow 37

information on the web. The gage was also outfitted with two video cameras that are triggered to 38

capture video once the river stage exceeds a predefined threshold. These cameras provide video 39

of underneath the bridge and also the bend upstream of the bridge, which is the focus of this 40

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effort, and can provide insight to engineers by capturing video evidence of flows and recording 1

potential erosional events on the banks. The video can also be analyzed with Large-Scale Particle 2

Image Velocimetry (LSPIV) software to calculate and map the surface velocity of the flows 3

upstream and downstream of the bridge. The LSPIV software is used to help calibrate and 4

confirm the gage’s velocity sensor along with computing the river discharge at the gage. All of 5

the sensors were deployed over a year in advance of planned construction and provided a 6

snapshot of the potential flow conditions at the Laguna Creek site. 7

The next objective included conducting an indirect measurement of discharge using 8

evidence from the flow that increased the bank erosion near the upstream bridge abutment prior 9

to gage installation. This indirect measurement resulted in a peak flow value of 1,300 cubic feet 10

per second. This discharge was compared with the U.S. Geological Survey program StreamStats, 11

which uses information from gages in the region to predict the flood flow frequency at ungaged 12

watersheds using basin characteristics, in this case, watershed area. This method predicts the two 13

year event to be 1,600 cubic feet per second [13]. In other words, a statistically common flow 14

event of 1,300 cubic feet per second caused the bank erosion on the bank upstream from the 15

bridge. After the gage’s installation, an additional flow event occurred on September 30th

, 2016, 16

which provided another opportunity to conduct an indirect measurement of discharge. This event 17

peaked at 1,270 cubic feet per second with a peak measured velocity under the bridge structure 18

of six feet per second. Again, this event was less than the predicted two year flow event using 19

StreamStats and continued to erode the bank next to the upstream bridge abutment. 20

Another interesting approach that the U.S. Geological Survey was able to utilize at the 21

Laguna Creek site was the use of ground-based Light Detection and Ranging (LiDAR) scans in 22

conjunction with photogrammetric surveys collected via small Unmanned Aerial Systems (sUAS 23

or drones). These data collection techniques are used to collect high resolution point clouds, 24

often under two centimeter resolution, to create three dimensional digital elevation models and 25

high resolution orthoimagery. The use of the terrestrial LiDAR system is beneficial under 26

structures and when very high resolution models are sought; the sUAS-based collection is best 27

for efficiently collecting topographic data over large areas (miles) and areas that are difficult to 28

survey using ground-based systems. These models can be collected before and after events to 29

both visualize and measure land surface changes and can be especially important when trying to 30

quantify erosional changes in stream channels. The land surface models can also be used in two 31

dimensional hydraulic modeling software as well as LSPIV software to both confirm and predict 32

different flow scenarios in the channel and around the bridge structure. Lastly, the high 33

resolution orthoimagery can be used to visualize current conditions at the site and can be used to 34

help inform decision making for the project. These technologies allow engineers to bring the site 35

into the office and can be very useful in planning and scoping scenarios. 36

This collaborative effort conducted by the Arizona Department of Transportation and the 37

U.S. Geological Survey was designed to provide snapshots of the potential hydrologic conditions 38

at Laguna Creek at the Highway 160 bridge site. Collecting data during the year prior to 39

construction provided a comprehensive data set including stream flow, river stage, surface 40

17


velocity, video capture of flows, and high resolution digital elevation models and orthoimages. 1

These data provide complete hydrologic monitoring that can be used by engineers and scientists 2

alike to better understand the hydrologic and hydraulic conditions at the Laguna Creek site, and 3

these data can be used to inform decision making for future construction efforts. These 4

instruments will be left in place post-construction for continued data collection, and the data can 5

be used to provide insight into the effectiveness of bank stability operations around the bridge 6

structure. 7

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ACKNOWLEDGEMENT 1

The authors wish to thank the people that supported this effort: ADOT State Engineer’s Office 2

and the ADOT Environmental Planning Group. The agencies that funded this effort: ADOT and 3

the Federal Highway Administration Sustainable Transport and Resilience Team. 4

5

REFERENCES 6

[1] Olmsted, S. Critical Assets and Extreme Weather Process & Lessons. Presented at the 7

Transportation Research Board National Conference on Transportation Asset 8 Management. April, 2014. 9

[2] Floodcast: A Framework for Enhanced Flood Event Decision Making for Transportation 10 Resilience. National Highway Cooperative Research Program 20-59(53) project 11 summary, 2015. 12

http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3725. 13 Accessed July 30, 2015. 14

[3] Olmsted, S., E. Lester. Arizona Department of Transportation (ADOT). United States 15 Geological Survey – ADOT Partnering Project meeting minutes summary. May, 2014. 16

[4] ADOT. Drainage Design Manual Volume 2, Hydrology Appendix D, Flood Frequency 17

Examples. 18

http://www.azdot.gov/docs/default-source/roadway-engineering-19

library/2014_adot_hydrology_manual_appendix_d.pdf?sfvrsn=2 20

Accessed July 30, 2015. 21

[5] Minimizing Roadway Embankment Damage From Flooding. National Highway 22

Cooperative Research Program 20-05 / Topic 46-16, Synthesis of Information Related to 23

Highway Problems solicitation summary, 2015. 24

http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3805 25


[6] FHWA. Climate Change & Extreme Weather Vulnerability Assessment Framework, Risk 27

Rating Matrix. Adapting to Rising Tides: Transportation Vulnerability and Risk 28

Management Assessment Pilot Project, November 2011. 29

http://www.fhwa.dot.gov/environment/climate_change/adaptation/publications_and_tools30

/vulnerability_assessment_framework/page03.cfm#Toc345418507. 31


[7] Olmsted, S., Gade, K. Climate Change and Extreme Weather Vulnerability Assessment 33

Pilot grant proposal and ADOT pilot project work plan. January 2013. 34

{8] ADOT. Preliminary Study of Climate Adaptation for the Statewide Transportation 35

System in Arizona. Report No. FHWA-AZ-13-696. 2014. 36

[9] ADOT. Extreme Weather Vulnerability Assessment Final Report. 1 of 19 FHWA Pilot 37

Project. January 2015. 38

[10] ASHTO and NCHRP. Direct material from the Research Problem Statement. Applying 39

and Adapting Climate Models to Hydraulic Design Procedures. Problem Number 2016-40

B-08. http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=4046 41

42

http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3725

http://www.azdot.gov/docs/default-source/roadway-engineering-library/2014_adot_hydrology_manual_appendix_d.pdf?sfvrsn=2

http://www.azdot.gov/docs/default-source/roadway-engineering-library/2014_adot_hydrology_manual_appendix_d.pdf?sfvrsn=2


http://www.fhwa.dot.gov/environment/climate_change/adaptation/publications_and_tools/vulnerability_assessment_framework/page03.cfm#Toc345418507

http://www.fhwa.dot.gov/environment/climate_change/adaptation/publications_and_tools/vulnerability_assessment_framework/page03.cfm#Toc345418507


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1

REFERENCES continued 2

[11] Block, Debra, and Redsteer, M.H., 2011, A dryland river transformed—the Little 3

Colorado, 1936–2010: U.S. Geological Survey Fact Sheet 2011–3099, 4 p., available at 4

http://pubs.usgs.gov/fs/2011/3099/ 5

[12] Graf, William L., 1984, A Probabilistic Approach to the Spatial Assessment of River 6

Channel Instability: Water Resources Research, Vol. 20, No. 7, Pages 953-962, July 7

1984. 8

[13] Paretti, N.V., Kennedy, J.R., Turney, L.A., and Veilleux, A.G., 2014, Methods for 9

estimating magnitude and frequency of floods in Arizona, developed with unregulated 10

and rural peak-flow data through water year 2010: U.S. Geological Survey Scientific 11

Investigations Report 2014-5211, 61 p., http://dx.doi.org/10.3133/sir20145211 12

13

FIGURES 14

[1] Figure 1. Project Hydraulic Report Final. ADOT. 2016 15

[2] Figure 2. Aerial SR 160 Laguna Creek Bridge. ADOT. 2016 16

[3] Figure 3. Project Hydraulic Report Final. ADOT. 2016. 17

[4] Figure 4. Project Design Overview. ADOT. 2016 18

[5] Figure 5. Photo, USGS. 2016. 19

[6] Figure 10. Photo, USGS. 2016. 20

[7] Figure 7. ADOT Cross Section. Drainage Manual. 2016. 21

[8] Figure 8. Hydraulic-related failure monitoring due to ground water, channel energy, and 22

altered flow. Photo ADOT. 2012. 23

[9] Figure 9. Risk Rating Matrix. ADOT. Preliminary Study of Climate Adaptation for the 24

Statewide Transportation System in Arizona. Report No. FHWA-AZ-13-696. 2014. 25

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http://pubs.usgs.gov/fs/2011/3099/

an arizona department of transportation -1 united states ... · 4 to this report, the total...

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